ISO 27001 A.8.24: encryption, explained for startups

A.8.24 Use of cryptography

Data is encrypted when stored and when it moves, and keys are managed safely. What proves it: encryption on stored data and connections, and keys kept in a key management service.

A certification auditor samples encryption settings and key management. A file that usually does the job: database and storage encryption settings, a scan of your domain's encrypted connections, and key rotation settings.

How to put it in place

Each step leaves a record, and the record is what the auditor samples rather than the step itself. Inside Polara, the control card for A.8.24 walks you through it in this order.

1. Turn on encryption for every database, storage bucket and disk.
2. Allow only encrypted connections.
3. Keep keys in a managed key service with rotation on.

The free ISO 27001 readiness assessment asks 3 questions that evidence it:

• Is data encrypted at rest?
• Is data encrypted in transit?
• Do you have a key management practice?

Policies, connectors and the SOC 2 overlap

In the ISO 27001 policy pack, the Cryptography and Key Management Policy covers A.8.24. An auditor reads the policy for the rule, then samples the records to see the rule was followed.

Connected systems that pull evidence for it:

• Amazon Web Services, S3 bucket encryption: server-side encryption at rest settings on each S3 bucket.
• Amazon Web Services, RDS instance encryption: storage encryption at rest for each RDS database.
• Amazon Web Services, KMS keys: customer-managed encryption keys per region.
• Google Cloud, Storage buckets: cloud Storage buckets with their default encryption at rest.
• Microsoft Entra ID, Intune managed devices: devices managed in Intune, with their encryption and compliance state.

The same evidence counts toward SOC 2. The Trust Services criteria that cover this ground: CC6.1, logical access and CC6.7, data in transit.

Technological controls

A.8.24 is one of the 34 technological controls in Annex A. The controls built into your systems: access, devices, malware, vulnerabilities, backups, logging, networks, encryption and secure development. Exports and settings screenshots prove most of them.

Nearby controls in the same theme:

• A.8.21, network services
• A.8.22, network segregation
• A.8.23, web filtering
• A.8.25, secure development
• A.8.26, application security needs
• A.8.27, secure architecture

Before it: A.8.23, web filtering. After it: A.8.25, secure development. Every control, by theme, is on the Annex A controls page.